1. Field of the Invention
The present invention relates to a recording method suitable for use in a digital data recording/reproducing apparatus for recording/reproducing digital data or the like to/from a tape-shaped recording medium.
2. Description of the Related Art
Since a tape streamer drive for recording/reproducing digital data to/from a magnetic tape has an enormous recording capacity, it is widely used to back up data stored in a storage device such as a hard disc or the like. The tape streamer drive is not only used for backup for a storage device but also suitable for recording large files such as motion picture data. As such a tape streamer drive, for example, a tape streamer drive of a helical scan type for recording/reproducing digital data to/from a magnetic tape by using, for example, a tape cassette similar to a tape cassette of an 8 mm VTR and using rotary heads is known.
In the tape streamer drive of the helical scan type, data is recorded to oblique tracks by two heads having different azimuth angles. For searching operation, to search a recording position of desired data, the tape is fed at a high speed and the data is reproduced at a high speed. When the high speed reproduction is executed, the heads scan over a plurality of tracks. While the tape is reproduced at a high speed as mentioned above, the search code is detected and while the search code and a target place are compared, the searching operation is executed.
As a method of recording the search code for searching operation, a method in which predetermined tracks are set to recording tracks of the search code and the search code is recorded in the whole track and a method in which recording areas of the search code is provided in a part of each track and the search code is recorded in the recording areas of the search code are considered.
The method in which the predetermined tracks are set to the recording tracks of the search code and the search code is recorded in the whole track has an advantage of high-speed search, because the search code can be certainly detected even in a high-speed reproducing mode. But it has a disadvantage that a recording efficiency of data is deteriorated, because the predetermined tracks are set to the recording tracks of the search code.
On the other hand, the method of the recording areas of the search code are provided in a part of each track and the search code is recorded in the recording areas of the search code, there is a case such that the search code cannot be detected at the time of the high-speed search, so that it is disadvantageous to the high-speed search.
Further, when the predetermined tracks are set to the recording tracks of the search code or when a part of each track is set to the recording areas of the search code as mentioned above, a process for detecting whether reproduction data is data in the search code areas or not is necessary, so that there is a problem such that the process is complicated.
It is, consequently, considered that the data is recorded on a sync block unit basis and the search code is recorded in each sync block. That is, the data is divided into a plurality of blocks and a sync and an ID are added to each block to thereby construct the sync block, and the data is recorded on the sync block unit basis.
When the data has been recorded on the sync block unit basis as mentioned above, a clock is reproduced from the sync of each sync block by a PLL and the data can be demodulated. By including the search code in the ID, therefore, the search code can be detected upon searching while the tape is reproduced at a high speed. Thus, since any special search code areas are unnecessary, the recording efficiency is improved. Since the search code is recorded in the whole area, it is advantageous for the high-speed search. Further, the process for detecting whether the reproduction data is that in the search code areas or not is unnecessary.
When the data is recorded on the sync block unit basis and the search code is included in each sync block as mentioned above, however, there is a case such that heads cannot pick up the sync blocks and the search code cannot be detected in dependence on the relation between the track pitch and the head width or the times speed or the like. There is also a case such that the searching operation cannot be certainly performed due to a detection error of the search code.